Semiconductor device fabrication is a process used to create integrated circuits that are present in many electrical and electronic devices. It is a multiple-step sequence of photolithographic, mechanical, and chemical processing steps during which electronic circuits are gradually created on a wafer made of semiconducting material. For example, during semiconductor device fabrication, numerous discrete circuit components, including transistors, resistors, capacitors, inductors, and diodes may be formed on a single semiconductor die.
A transistor is a semiconductor device with many uses. Generally speaking, a transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. Typically, a voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. One common type of transistor is a metal-oxide-semiconductor field-effect transistor (MOSFET). A typical MOSFET comprises an insulated gate, whose voltage determines the conductivity of the device as seen between two other non-gate terminals of the device, known as a drain terminal and source terminal. The MOSFET's ability to change conductivity with the amount of applied voltage allows it to be used for amplifying or switching electronic signals.
A type of MOSFET seeing increased use is an extended-drain MOSFET, sometimes referred to a drain-extended MOSFET, EDMOS, or DEMOS. An extended-drain MOSFET, as implied by its name, extends the drain of a transistor device by adding an n-type drain drift region between the drain and the channel of the transistor device, which may trap a majority of the electric field in this extended-drain region instead of the channel region, therefore containing hot carrier effects to this extended-drain region, instead of the channel region, therefore increasing hot carrier reliability of the transistor device. Existing extended-drain MOSFET devices often present a tradeoff between their drain-to-source (Vds) breakdown voltages and their on resistance (Rdson). Accordingly, MOSFET devices that reduce such tradeoff are desired.